The subjunctive mood communicates wishes, hopes, requirements, or statements that express an unreality.
We have subjunctive statements in modern English; they're just not inflected, so those verbs look exactly the same as non-subjunctive verbs. The only typical subjunctive phrase left standing after all this time is were, which is the subjunctive mood of the verb to be.
If you've tried learning a romance language, you hate the subjunctive mood.
Along with the phrase I were—as in If I were a billionaire, I would own my own zeppelin—you'll also see the subjunctive used in clauses beginning with that and expressing something desired, recommended, or necessary.
They often follow verbs such as insist or demand, adjectives such as necessary or desirable, and nouns such as recommendation or essential.
" If the bagpiper we hired for our St. Patrick's Day party were to show up, we would light a fire and pass around a flagon of ale as we listened to him. "
A fireplace and a flagon of ale? Sounds cozy. That wishful thinking is key to spotting the subjunctive mood, which expresses a wishful or hopeful attitude toward something that may or may not be true. Other clues to this mood are were (the subjunctive form of to be), the word if, and the conditional verb would in the clause following the subjunctive verb. Now if only that bagpiper would show up.
" If I were an Olympic swimmer, I would eat ten chocolate chip banana pancakes every morning."
This sentence begins with the subjunctive verb were, which is then followed by a statement using the wishful word would.
" Since I am graduating tomorrow, it's especially important that I not be out late tonight."
In this example, the phrase that I not be out late tonight uses the verb be in the subjunctive mood as it points out a circumstance that is both desirable and necessary. You probably won't be able to walk at graduation if you're still sleeping. The late night is for the day of graduation.
We're not going to get too detailed here. Just remember: it's "I wish I were.